1. Field of the Invention
This invention is directed to improvements in processes for the selective cracking of dialkylbenzene compounds. It is particularly concerned with increasing the yield of recyclable cracking products of such selective cracking processes.
2. Description of the Prior Art
It has been known and demonstrated that certain shape selective crystalline zeolite catalysts are useful to selectively react the 1,4-isomer of dialkylbenzene compounds in preference to the 1,2- and/or 1,3-isomers. This technology is found to be of significance in the production of 1,3-dialkylbenzenes, since the 1,4-isomer is normally co-produced with the 1,3-isomer and must therefore be removed. Since the boiling points of these isomers are frequently too close together to permit satisfactory fractional distillation on a commercially viable scale, the selective cracking of the undesired 1,4-isomer to the total or near-total exclusion of the 1,3-isomer would be of significant importance.
In such selective cracking reactions it is desirable that the alkyl group be removed intact from the aromatic ring, thereby regenerating the starting olefin and aromatic compounds which in turn may then be recovered and recycled to produce more dialkylbenzene. Unfortunately, what frequently happens is that the alkyl group, once it is removed from the aromatic ring, continues to react on the catalyst to give a spectrum of light hydrocarbons with no recoverable major components.